Apparatus and method for speed and strip tracking control



July 2, 1957 D. A. M ARTHUR ETAL Filed Jan. 5, 1955 2 Sheets-Sheet l el it.

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I0 25% 2 LJ N a) 4 N fl fl r f INVENTORS Donald A. McArthur 8 By Albert R. Geiszler y 1957 D. A. MGARTHUR EFAL 2,797,918

7 APPARATUS AND METHOD FOR SPEED AND STRIP TRACKING CONTROL Filed Jan. 3, 1955 H 2 Sheets-Sheet 2 l 38 39 Q 52 I INVENTORS Donald A. McArthur a BY Albert R. Geiszler States Patent Oflice Patented July 2, 1957 APPARATUS AND METHGD FOR SPEED AND STRIP TRACKING CONTROL Donald A. lWcArthur and Albert R. Geiszler, Warren,

Ohio, assignors to The Wean Enginee Company, Inc, Warren, Ohio, a corporation of Ohio This invention relates to the control of the speed of rolls in a strip treatment line whereby the tracking of the strip in passing over the rolls may be improved.

In a strip treatment line, the strip to be treated is normally passed over a plurality of deflector means through various treatment tanks or sections. customarily, the deflector means comprise rolls which are journaled for rotation and over which the strip passes as it goes through the various treatment sections of the line. The rolls cause the strip to pass back and forth in generally parallel planes as it passes through the various tanks. Some or all of the deflector rolls may be driven by power means. Normally, the power supplied to the deflector rolls is sufficient only to overcome friction in the roll bearings and to flex the strip passing over the rolls. In such cases the strip is pulled through the line from a bridle at the end of the line.

In electrolytic tin plating lines, for example, it is highly desirable, to insure even and regular plating along the edges, that the strip should track. Stated in other words, it is desired that each part of the strip should follow in the path of what has passed before without wandering or weaving from side to side as it passes over the rolls. It has been found, however, in some strip lines that the strip tends to weave from side to side on the rolls.

conventionally it has been the practice to synchronize the speed of all of the driven deflector rolls in a strip line so that their circumferential speed is equal to the speed of the strip. We have discovered that tracking of strip in a strip line can be improved by selectively regulating the speed of the deflector means in the strip line relative to the speed of the strip over these means. We preferably employ rolls whose speed may be regulated relative to the speed of the strip to achieve the best tracking. It is conceivable that the best tracking may be achieved when the surfaces of the deflector rolls are rotating slower than the strip passing around the rolls or when the surfaces of the deflector rolls are rotating faster than the strip passing around the rolls.

We provide means by which the speed of the deflector rolls relative to the strip may be selectively varied, and means to automatically maintain the speed of the deflector rolls constant relative to the speed of the strip.

We provide means to measure the speed of the strip through the line, means to measure the speed of at least one of the deflector rolls, means to combine signals from the speed measuring means, and control means to regulate the speed of the deflector rolls in accordance with the combined signals. We preferably provide means whereby the signal corresponding to the speed of the strip and the signal corresponding to the speed of the deflector rolls may be varied relative one to the other. We further preferably provide means for regulating the eifective signal produced by signal means associated with each deflector roll.

Other details, objects and advantages of our invention will become apparent as the following description of cer- 2 tain present preferred methods of practicing the invention proceed.

In the accompanying drawings we have illustrated certain present preferred methods of practicing the invention in which Figure 1 is a diagrammatic illustration of the preferred embodiment of our apparatus; and

Figure 2 is a diagrammatic illustration of a modification thereof.

Referring to Figure l, strip 1 is passed through a strip line over a plurality of idler deflector rolls 2, a freely rotatable reference roll 3 and three driven deflector rolls 4, 5 and 6. It will be understood that the illustration of the strip line is purely diagrammatic and that the strip might be passing, for example, through a series of electrolytic plating tanks, pickling tanks or cleaning tanks. It will be further understood that the number of deflector rolls is not limited as shown in the drawing but might be any convenient number. Coupled to reference roll 3 is a generator tachometer 7 supplying direct current at a voltage which is proportional to the speed of reference roll 3. One terminal of tachometer 7 is connected directly to terminal 8. The other terminal is connected to terminal 3 through resistor 9 thus making a closed loop outside tachometer 7 through terminal 8 and resistor 9. A movable contact 10 connects any desired point on resistor 9 to terminal 11 of amplifier 12. Coupled to deflector rolls 4, 5 and 6 are generator tachometers 13, 14 and 15, respectively. These are similar to tachometer 7 and each will produce a direct current voltage proportional to the speed of the coupled deflector roll. Tachometer 13 has its terminals connected to points 16 and 17. Between one terminal and point 16 is a resistor 18. Point 16 is connected to lead 19 through resistor 20. Point 17 is connected to lead 21 through resistor 22. A resistor 23 is connected between points 16 and 17. Sliding contact 24 allows any desired portion of resistor 23 to be bypassed. Tachometers 14- and 15 are connected by similar circuits to leads 19 and 21. The three tachometer-s 13, 14 and 15 are in parallel. Lead 19 is connected to terminal 8. Lead 21 is connected to terminal 25 of amplifier 12.

Amplifier 12 is of conventional design and may be a rotating, electronic, or magnetic amplifier, or any combination thereof. It will control the current in field coil 26 of direct current generator 27 in response to the voltage impressed across terminals 11 and 25. Generator 27 supplies current to direct current motors 28, 29 and 30, coupled respectively to deflector rolls 4, 5 and 6. The field coil 31 of motor 28 is connected between bus bar 32 and ground. A resistor 33 is placed in the circuit in series. A sliding contact 34 allows current to be shunted around any part of or all of resistor 33. The field coils of motors 29 and 30 are similarly connected.

Referring now to Figure 2 we have shown a modification of the preferred embodiment of our apparatus. Strip 35 passes over a freely rotatable reference roll 36 and a single driven deflector roll 37. As in Figure l the strip and the rolls are shown only diagrammatically. A generator tachometer 38 is coupled to reference roll 36 and will produce a direct current voltage proportional to the speed of reference roll 36. One terminal of tachometer 38 is connected to point 39. The other terminal is connected to point 39 through resistor 40. A generator tachometer 41 is coupled to deflector roll 37 and produces a direct current voltage proportional to the speed of deflector roll 37. One terminal of tachometer 41 is coupled to point 39. The other terminal is connected to terminal 42 of amplifier 43. Amplifier 43 is of conventional design and may be a rotating, electronic, or magnetic magnifier, or a combination thereof. Terminal 44 of amplifier 43 is connected to movable contact 45 which will make contact with resistor 40 at any given point. I

Amplifier 43 will produce a voltage on field coil 46 of direct current generator 47 in response to the voltage impressed on terminals 42 and 44. Generator 47 supplies current to direct current motor 48 which is coupled to deflector roll 37. The field coil 49 of motor 48 is connected between bus bar 50 and ground through resistor 51. Sliding contact 52 allows any part of resistor 51 to be shunted.

In operation (referring now to Figure 1) strip 1 will be drawn through the line by drive means at the end of the line (not shown in the drawings). As it passes through the line it will cause reference roll 3, which is freely rotatable, to revolve so that the circumferential speed of the roll is equal to the speed of the strip. This will cause tachometer 7 to produce a potential proportional to the speed of the strip. At the same time deflector roll 4 will be rotating at the speed at which it is driven by motor 28. The circumferential speed of deflector roll 4 will not necessarily be the same as the linear speed of the strip. Tachometer 13 will produce a signal proportional to the rotative speed of deflector roll 4. For any given adjustment of sliding contact 24 on resistor 23 the potential between points 16 and 17 will be proportional to the speed of deflector roll 4. Tachometers 14 and 15 will develop signals in a like manner. The voltages from each of the tachometers 13, 14 and 15 will be imposed on leads 19 and 21. Should tachometer 13, for example, be developing a lower voltage than the others there will be a tendency for a circulating current produced by tachometers 14 and 15 to pass through resistors 20, 22 and 23 so that the standing voltage on leads 19 and 21 will be the average of the voltages supplied to the leads by tachometers 13, 14 and 15. It is apparent that terminal 8 and lead 19 must be at the same potential. Thus terminal 8 and terminal 25 of amplifier 12 will have the same potential difference as leads 19 and 21. If the voltage drop between movable contact 10 and terminal 8 caused by tachometer 7 is equal to, but opposed to, the voltage across leads 19 and 21 there will be no voltage drop across terminals 11 and 25 of amplifier 12. At this point the system will be in balance and the amplifier will maintain the existing voltage on field coil 26. The result will be that motors 28, 29 and 30 will continue to drive deflector rolls 4, 5 and 6 at the same speeds relative to the speed of the strip.

Should the speed of the strip be increased, tachometer 7 will produce a greater voltage and there will be a voltage imposed across terminals 11 and 25. The amplifier will increase the current in field coil 26, causing a greater current to be supplied to motors 28, 29 and 30. This will cause the speed of the motors and coupled deflector rolls to increase, and tachometers 28, 29 and 30 will supply a higher voltage to the control circuit. When the speed of the driven deflector rolls has again reached the same speed relative to the strip, the circuit will again balance with no voltage across terminals 11 and 25. The amplifier will then maintain the current in coil 26 constant. Should the strip be slowed down, then a voltage of reverse polarity would be imposed upon terminals 11 and 25 and the amplifier will reduce the current in field coil 26 until the signal circuit is again in balance.

In order to secure better tracking it may be desirable to change the circumferential speed of deflector rolls 4, 5 and 6 relative to the speed of the strip. The best tracking is not always secured when the deflector rolls have their circumferential speed equal to the speed of the strip. It may be desired at any time to vary the relative difference in speed to secure the best tracking. This may be done by adjusting movable contact 19 so that the voltage drop between terminal 8 and movable contact 10 is larger or smaller. This will cause a voltage, whose polarity will depend upon the direction in which contact 1.0 is moved, across terminals 11 and 25 of amplifier 12. The amplifier will increase or decrease the current in field coil 26 according to the polarity of the voltage between terminals 11 and 25. This will cause a greater or lesser voltage to be generated and will increase or decrease the current through the armatures of motors 28, 29 and 31). As the current in coil 26 is increased or de creased the motors will drive deflector rolls 4, 5 and 6 at a higher or a lower speed. At the same time the voltage generated by tachometers 13, 14 and 15 will be increased or decreased. At such time as the voltage between terminal 8 and terminal 25 generated by tachometers 13, 14 and 15 again equals the voltage between terminal 8 and movable contact 10 produced by tachometer 7, amplifier 12 will again hold the current in field coil 26 constant. It will be obvious that should the strip exert a pull on one of the deflector rolls, the coupled motor would act as a generator and brake the deflector roll.

As the line is in use over long periods of time there will be wear upon the rolls, and as they wear they will be removed and redressed. This will cause the roll which has been redressed to be of somewhat smaller diameter. Therefore, for a given circumferential speed of the roll, the rotative speed will have to be slightly higher. This will cause the attached tachometer to produce a higher voltage since its voltage output is a function of its own speed. Adjustment of sliding contact 24 on resistor 23 will vary the voltage across points 16 and 17. As more of resistor 23 is by-passed the current between points 16 and 17 will become greater. This will cause a voltage drop across resistor 18 and reduce the voltage across points 16 and 17. Thus, for any given speed of the tachometer, the effective voltage delivered to the circuit may be decreased. Conversely, the tachometer can be adjusted to deliver the same effective voltage at some higher speed. Since a similar circuit is provided for each of the tachometers coupled to a deflector roll, compensation may thus be made for a reduction in the diameter of any deflector roll. The voltage imposed upon leads 19 and 21 by each deflector roll tachometer will thus be representative of the circumferential speed of the coupled deflector roll.

To compensate for variations from one drive motor to another, the current through field coil 31, for example, may be varied through use of sliding contact 34. In this manner the field strength of the motor may be varied and with it the speed of the motor for a given armature current. Similar arrangements are provided for motors 29 and 30.

Referring now to Figure 2 the output of tachometer 41 is matched directly against the output of tachometer 38. The terminals of tachometer 41 are connected to the terminal 42 of amplifier 43 and to terminal 39. Tachom- V eter 38 is coupled directly against this and incorporates resistor 40 in its circuit. By adjustment of movable contact 45 the two tachometer voltages may be matched against one another in varying ratios. There is no need for an additional circuit to compensate for changes in the diameter of roll 37 since there is only one driving roll tachometer feeding into the circuit. When roll 37 is decreased to a smaller diameter the result will be to change the position of movable contact 45 for which roll 37 will be synchronized with strip 35. In other words, the zero position of movable contact 45 will be altered by a change in the diameter of the deflector roll. The resultant signal is placed upon terminals 42 and 44 of amplifier 43. Amplifier 43 operates in regulating motor 48 identically with amplifier 12 in regulating motors 28, 29 and 30 in that it will act to keep the current in field coil 46 matched to the voltage across terminals 42. and 44. The current in field coil 49 is adjustable to provide further individual adjustment of motor 48.

While we have shown and described certain present preferred embodiments of our invention, it is to be distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied within the scope of the following claims.

We claim:

1'. A speed control system for a strip line having strip driven means and strip deflector means, first signal means responsive to the speed of said strip driven means, second signal means responsive to the speed of said strip deflector means, means to combine the signal from said first signal means and said second signal means into a single resultant signal, separate deflector drive means, and control means responsive to said signal to control said deflector drive means.

2. A speed control system for a strip line comprising first signal means producing a signal corresponding to the speed of the strip through the line, at least one deflector member, second signal means to measure the speed of each deflector member, means to combine the signals from said first signal means and said second signal means into a resultant signal, and means to vary the speed of each deflector member in accordance with the resultant signal.

3. A speed control system for a strip line having strip driven means and strip deflector means, power means driving said deflector means, first signal means separate from said power means responsive to the speed of said strip driven means, second signal means separate from said power means responsive to the speed of said strip deflector means, means to combine the signals from said first signal means and said second signal means into a single resultant signal, and control means responsive to said signal to control said power means.

4. A speed control system for a strip line comprising first signal means producing a signal corresponding to the speed of the strip through the line, at least one deflector roll, power means driving the deflector rolls, second signal means separate from said power means to measure the speed of the deflector rolls, means to combine the first signal means and the second signal means into a resultant signal means to vary the strength of the signal from one signal means relative to the strength of the signal from the other signal means, and control means eflective to regulate the power means in response to the resultant signal.

5. A speed control system comprising a driven roll, a plurality of deflector rolls, drive means driving the deflector rolls, a speed sensitive means coupled to said driven roll and to each of said deflector rolls, said speed sensitive means being separate from said drive means each of said speed sensitive means producing a signal, means for combining the signals from the speed sensitive means into a single resultant signal, and means to vary the speed of said drive means in accordance with the resultant signal.

6. A speed control system for a strip line having a reference roll driven by the strip, a plurality of driven deflector rolls, drive means for each of said deflector rolls, tachometer means coupled to the reference roll and producing an electrical potential corresponding to the speed of the reference roll, tachometer means coupled to each of the deflector rolls and each producing an electrical potential corresponding to the speed of the associated deflector roll, means to vary the effective potential produced by each tachometer means coupled to a deflector roll, means for combining all of the potentials from the tachometer means coupled to the deflector rolls into a single deflector roll potential, means for combining the deflector roll potential with the potential from the reference roll tachometer means into a resultant potential, and control means responsive to said resultant potential to vary the speed of the said drive means.

7. A speed control system for a strip line having a reference roll driven by the strip, a plurality of driven deflector rolls, drive means for each of said deflector rolls, tachometer means coupled to the reference roll and producing an electrical potential corresponding to the speed of the reference roll, tachometer means coupled to each of the deflector rolls and each producing an electrical potential corresponding to the speed of the asso ciated deflector roll, means to vary the effective potential produced by each tachometer means coupled to a deflector roll, means for combining all of the potentials from the tachometer means coupled to' the deflector rolls into a single deflector roll potential, means for combining the deflector roll' potential with the potential from the reference roll' tachometer means into a resultant potential, means to vary the amount of the potential produced by the reference roll tachometer means which is available for combining with the deflector roll potential, and con trol means'responsive to said resultant potential to vary the speed of the said .drive means.

8. A speed control system for a strip line having a reference roll driven by the strip, a plurality of deflector rolls, drive means for each of said deflector rolls, tachometer means coupled to the reference roll and pro ducing an electrical potential corresponding to the speed of the reference roll, tachometer means coupled to each of the deflector rolls and each producing an electrical potential corresponding to the speed of the associated deflector roll, means to vary the eflective potential produced by each tachometer means coupled to a deflector roll, means for combining all of the potentials from the tachometer means coupled to the deflector rolls into a single deflector roll potential, means for combining the deflector roll potential with the potential from the reference roll tachometer means into a resultant potential, means to vary the strength of the two potentials combined into the resultant potential relative to one another, and control means responsive to said resultant potential to vary the speed of said drive means.

9. A speed control system for a strip line having a reference roll driven by the strip, at least one deflector roll, drive means for each deflector roll, speed sensitive means coupled to the reference roll and producing a signal corresponding to the speed of the reference roll, speed sensitive means separate from said drive means coupled to each deflector roll and producing a signal corresponding to the speed of the coupled deflector roll, means for combining all of said signals into a resultant signal, control means responsive to said resultant signal to vary the speed of said drivemeans, and additional speed control means whereby the speed of each of said drive means may be separately varied.

10. Means for controlling the speed of rolls in a continuous strip line comprising a reference roll driven by the strip, a deflector roll, driving means coupled to the deflector roll, tachometer means coupled to the reference roll and producing a potential corresponding to the speed of the reference roll, second tachometer means coupled to the deflector roll and producing a potential correspond ing to the speed of the deflector roll, means for combining the potential produced by the deflector roll tachometer means and a selective amount of the potential produced by the reference roll tachometer into a resultant potential, and control means to vary the speed of the deflector means in accordance with the resultant potential.

11. Means for controlling the speed of rolls of a continuous strip line comprising a reference roll driven by the strip, a plurality of deflector rolls, power means coupled to the deflector rolls, tachometer means coupled to the reference roll and producing a potential corresponding to the speed of the reference roll, tachometer means coupled to each deflector roll and each producing a potential corresponding to the speed of the associated deflector roll, means for combining the potentials produced by the deflector roll tachometer means with a selective amount of the potential produced by the reference roll tachometer into a resultant potential, and control means eflective to regulate the speed of said drive means in accordance with the resultant potential.

12. Means for controlling the speed of rolls in a continuous strip line comprising a reference roll driven by the strip, a plurality of deflector rolls, power means driving each of the deflector rolls, signal means connected to the reference roll and producing a reference roll signal corresponding to the speed of the reference roll, signal means separate fromsaid power means connected to each of the deflector rolls and producing a signal corresponding to the speed of the deflector roll, means to combine all of the signals from the deflector roll signal means into a single deflector roll signal, means to combine the deflector roll signal and the reference roll signal into a resultant signal, means to vary the reference roll signal eflective for combination with the deflector roll signal, and control means effective to regulate the speed of the power means in accordance with the resultant signal.

13. Means for controlling thelspeed of rolls in a continuous strip line comprising a reference roll driven by the strip, a plurality of deflector rolls, power means driving each of the deflector rolls, signal means connected to the reference roll and producing a reference roll signal corresponding to the speed of the reference roll, signal means separate from said power means connected to each deflector roll and producing a signal corresponding to the speed of the deflector roll, means to combine all of the signals from the deflector roll signal means into a single deflector roll signal, means to vary the signal from each deflector roll signal means effective for combination into the deflector roll signal, means to combine the deflector roll signal and the reference roll signal into a resultant signal, means to vary the reference roll signal eflective for combination With the deflector roll signal, and control means effective to regulate the speed of the power means in accordance with the resultant signal.

14. Means for controlling the speed of rolls in a continuous strip line comprising a reference roll driven by the strip, a plurality of deflector rolls, power means driving each of the deflector rolls, signal means connected to the reference roll and producing a reference roll signal corresponding to the speed of the reference roll, signal means separate from said power means connected to each of the deflector rolls and producing a signal corresponding to the speed of the deflector roll, means to combine all of the signals from the deflector roll signal means into a single deflector roll signal, means to vary the signal from each deflector roll signal eflective for combination into the deflector roll signal, means to combine the deflector roll signal and the reference roll signal into a resultant signal, means to vary the reference roll signal effective for combination with the deflector roll signal, control means effective to regulate the speed of the power means in accordance with the resultant signal, and means to separately regulate the speed of each power means.

15. The method of regulating the tracking of strip in a line which comprises measuring the speed of the strip through the line, passing the strip over at least one deflector roll in the line, and selectively regulating the speed of the deflector rolls to maintain a differential between the speed of the strip and the peripheral speed of the deflector rolls.

16. The method of improving the tracking of strip in a line which comprises measuring the speed of the strip through the line, passing the strip over a plurality of deflector rolls in the line, and selectively regulating the circumferential speed of the deflector rolls relative to the speed of the strip maintaining a selected differential between the circumferential speed of the rolls and the speed of the strip.

17. In a strip line, speed control means comprising signal means producing an electric signal corresponding to the strip speed through the line, at least one strip deflector roll, drive means for each such deflector roll, separate signal means producing an electric signal corresponding to the speed of each such deflector roll, means to combine all of said signals into a single resultant signal, and means to control said drive means according to the resultant signal.

18. In a continuous strip line, speed control means comprising signal means producing an electric signal corresponding to the strip speed through the line, at least one strip deflector roll, a drive motor for each such deflector r011, separate signal means producing an electric signal corresponding to the speed of each such deflector roll, means to combine all of said signals into a resultant signal, and means to control each said drive motor in accordance with the resultant signal.

19. The method of controlling the tracking of strip in a strip line which comprises measuring the speed of the strip through the line, passing the strip over at least one deflector roll in the line, and maintaining the peripheral speed of each said deflector roll at a speed diflerent from the speed of the strip through the line.

References Cited in the file of this patent UNITED STATES PATENTS 1,553,626 Motter Sept. 15, 1925 1,561,265 Menzies Nov. 10, 1925 1,563,452 Stoltz Dec. 1, 1925 2,165,127 Carnegie July 4, 1939 2,599,517 Raspet June 3, 1952 FOREIGN PATENTS 506,398 Great Britain May 26, 1939 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,797,918 July 2, 1957 Donald A. McAI-thur et a1.

Column 5, line 3'7, after 'signal" insert a commaa Signed and sealed this 17th day of September 1957,

(SEAL) At'fiest: KARL H. AXLINE ROBERT C. WATSON ttes i g icer onmissioner of Patents 

